Before we get into Bayesian network (BN) concepts, we should be aware of the theories of probability. So, we will try to touch upon them and build the foundation of BNs.

We already know that probability is the degree of certainty/uncertainty of an event occurring. However, it can be also termed as the degree of belief, which is more commonly used when we talk about BN.

When we toss a fair coin, we say that the degree of belief around the event of heads/tails happening is 0.5. It implies that our belief of heads happening is as strong as tails. The probability can be seen as follows:

p(Heads)=p(tails)=0.5

In this chapter, we will cover the following topics:

• Bayesian rules
• Bayesian networks